1. Field of the Invention
The present invention relates to the field of establishing computer networks using cable modems. Specifically, the present invention allows a client, communicating with a server using separate upstream and downstream devices, to detect the presence of upstream traffic and automatically initiate a dial-up connection with the server.
2. Description of Related Art
Currently, most home personal computers (clients) are connecting with the Internet and other on-line services using the public telephone network. Most often, data is transferred using Transmission Control Protocol/Internet Protocol (TCP/IP) implemented over such protocols as the Point-to-Point Protocol (PPP) or Serial Line IP (SLIP). PPP and SLIP allow clients to become part of a TCP/IP network (such as the internet) using the public telephone network and either an analog modem or an Integrated Services Digital Network (ISDN) device. Clients connect to a network by "dialing-up" a Point of Presence (POP), or "headend", server, which then assigns the client an IP address.
The public telephone network has a switched point-to-point architecture and only offers relatively low bandwidth as it was originally designed for analog voice communication. Thus, it does not scale well to the delivery of broadband data such as multimedia. As a result, there are several efforts to create a broadband data delivery infrastructure for client applications. Such an infrastructure, when combined with the increasingly powerful clients that are now available, will enable the delivery of rich multimedia programming to the home.
Broadband data delivery may be accomplished over a variety of different delivery infrastructures. Of these, perhaps the most promising is the infrastructure currently used to deliver cable television. Recent advancements in radio frequency modulation and demodulation technology, along with a large base of cable television subscribers, has made cable television service providers a strong candidate for becoming the preferred provider of broadband services to the home. In the broadband network architecture, a client will be continuously connected to the broadband network and will be in communication with one or more headend servers at all times.
However, as the cable television network was originally intended only for transmitting data from a headend server located at the cable television service provider's site to one or more subscribers/users (i.e., the network was designed for a one-to-many transmission of information), no provision was made for receiving data from the equipment (i.e., clients) located at the users' locations.
A solution has been proposed to achieve two-way communication of data using the existing cable television infrastructure. "Downstream data", defined to be data sent from a headend server to a client, is transferred over coaxial cable from the headend server into the home and to the user's client PC, while "upstream data", defined to be data sent from the client to the headend server, is transferred over the public telephone network. The asymmetrical allocation of upstream/downstream bandwidth is acceptable for most applications as the majority of users requires a larger downstream bandwidth compared to the upstream bandwidth (i.e., most users are "data consumers" rather than "data generators").
In operation, downstream data is received by a client using a "one-way" cable modem while upstream data is transmitted by an analog modem or an ISDN device, over the public telephone network, to the headend server via a Plain old Telephone Service (POTS) server at the headend office. The POTS server forwards any upstream data sent by the client to the headend server for appropriate action (e.g., providing domain name server (DNS) services, simple mail transfer protocol (SMTP) services, gateway or proxy services, etc.).
The client and the headend server communicate using TCP/IP. Data is transmitted in packets, where packets are defined as a block of data with appropriate transmission data attached in the form of a header and footer to be sent or received over a network. Downstream and upstream data are sent using the ethernet standard, as defined by the Institute of Electrical and Electronics Engineers (IEEE) 802.3, modulated for transmission over: (1) coaxial cable using the cable modem; or, (2) a telephone line using the analog modem or the ISDN device and PPP or SLIP protocols.
In order for the client to use the cable modem for communication, the cable-modem is installed as an Ethernet adapter in the client, and the client is configured just as an ordinary TCP/IP network machine. After the initial configuration and initialization of the cable modem, data would come from the headend server over the coaxial cable in the cable network.
In addition to having separate devices for upstream and downstream data transfers, a client will be said to be "multi-homed" in that the client's upstream device and its downstream device will both have different IP addresses as the upstream device (i.e., the analog modem or ISDN device), will be assigned an IP address in addition to the IP address already assigned to the cable modem. In the multi-homed environment, all upstream data will be sent to the IP address of the upstream device while all downstream data will be received from the IP address of the downstream device.
Before multi-homing of the client's TCP/IP stack takes place, all packets (data frames) being sent by the client will be delivered to the downstream device (i.e., the cable modem) for transmission to the headend server. However, as the cable modem does not support transmission of upstream data, the cable modem cannot transmit the packets, and as a result, the packets are lost. After multi-homing of the client's TCP/IP stack takes place, upstream data will be sent using the upstream device (i.e., the analog modem on ISDN device) while downstream data will still be received over the cable modem.
Currently, in order for the client to become multi-homed and capable of sending data back to the headend server, a user would need to manually "dial-up" (i.e., the user has to initiate a connection to) the headend server using functions such as those provided by the Remote Access Services (RAS) library provided by Microsoft.RTM. Corporation in its Windows NT.RTM. and Windows 95.RTM. operating systems. Once the connection is established, the TCP/IP stack becomes multi-homed and any data that needs to go upstream would go over the public telephone network while any data that needs to come downstream still comes over the coaxial cable.
Although attempts have been made to provide for the automatic initiation of an upstream connection (i.e., the initiation of a dial-up of the headend server) to establish multi-homing of the client and the establishment of an upstream data path, most of the attempts have been proprietary to specific applications and are not available to all applications in a transparent and efficient manner.
Therefore, a solution needs to be provided for the above-identified situation where a client PC has a dial-up for separate upstream traffic and it is desired that whenever the user launches any network application, the upstream connection is established automatically, without any user intervention.